open ur firefox,in address bar type
check whether plugins are installed.
U hv to install java,mozplugger,totem-plugin,mozilla-mplayer,flash-plugin-nonfree,realplayer etc from synaptic pkg manager.
search for good repos.
As ur running Debian-let's jump ahead and use Sid(unstable repo).It sure Rocks!!
check
http://debian-unofficial.org/
is a good repo.